'X' and 'Y' are the components of Binomial nomenclature. This naming system was proposed by 'Z':
A X-Generic name, Y-Specific epithet, Z-Carolus Linnaeus
B X-Specific epithet, Y-Generic name, Z-R.H. Whittaker
C X-Specific epithet, Y-Generic name, Z-Carolus Linnaeus
D X-Generic name, Y-Specific epithet, Z-R.H. Whittaker